WireGaugeCalc Free calculator · NEC cited · works offline
Page Wire Size Calculator
Page wire size calculator is fast with WireGaugeCalc, since you enter the load amps, conductor material, and termination temperature and read the gauge.
The calculator matches your ampere load to the NEC 310.16 column for 60, 75, or 90 degree C terminations so the result fits the breaker and the lugs.
Size the conductor right here on the page and move to your pull with a number you can trust.
Open the calculatorSmallest conductor whose ampacity meets the load, NEC Table 310.16. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Sizing Romex and THHN with a romex gauge voltage calculator
Enter the continuous load and the tool applies the 125 percent factor before it reads the 310.16 table.
Pick copper or aluminum and the gauge shifts, since aluminum carries less current at the same size.
The result lists the AWG that meets the ampacity column for your chosen termination temperature.
What the calculator checks
Each input maps to one NEC requirement:
- Load in amps, with the 125 percent continuous-load bump applied
- Copper or aluminum conductor material
- Termination rating at 60, 75, or 90 degrees C
- NEC 310.16 ampacity for the matched gauge
- A note when temperature correction or bundling derating may apply
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
Why does the result use the 75 degree C column instead of 90?
Most breakers and lugs are listed for 75 degrees C, so the conductor is sized to that column even when the insulation is rated 90 degrees C. Confirm the termination rating stamped on your equipment, and verify against the current NEC and your local authority having jurisdiction.
Can I size Romex with this tool?
Yes, treat NM-B cable as 60 degree C conductors per NEC 334.80 and select copper at the 60 degree column. The romex gauge voltage calculator path will then show the gauge that meets that limited ampacity.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.